The subject matter of the present invention relates generally to electrical attenuators and switching therefor, and in particular to a programmable step attenuator apparatus.
Previous high-impedance programmable attenuators have been of the rotary or turret type and have utilized electro-mechanical switching means. Such attenuators are relatively expensive, and suffer from the problems of low reliability and relatively low performance. One attempt to overcome the problem of low performance associated with turret-tupe attenuators is the apparatus disclosed in U.S. Pat. No. 3,753,170, wherein hybrid passive attenuator elements are mounted on a circuit board and the switching is accomplished therebetween by means of camactuated circuit-board-mounted contacts. However, such an attenuator does not lend itself to programmability, and further the contacts are susceptible to the same problems incurred in turret-type attenuators, that is, pitting, wear, uneven surface contact, oxidation, and dirt. While designed for extremely high frequency operation, the foregoing undesirable conditions have a detrimental effect on such performance.